Proceedings Paper

X-ray phase-retrieval algorithms are widely exploited in contemporary diffraction techniques to image at the nanoscale.
Often reconstruction of the sample shape (image) suffices for the purpose of experiment. Identification of specimen
composition requires a quantitative profiling of the complex refractive index. We show that the diffraction effects from
the experimental setup and artifacts from the phase-retrieval algorithms themselves are comparable with the diffraction
contrast that is experimentally observable from thin specimens with very low electron density. We show that, based on
the analysis of application of the relevant phase-retrieval methods, there is a lower limit in optical density, which can be
reconstructed using the existing phase-retrieval methods. This limit appears to be imposed by real-life experimental
conditions and the intrinsic artifacts of the phase-retrieval techniques.